style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    background-color: #ecf0f3;
    font-family: sans-serif;
    /* overflow: hidden; */
}

.container {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.calculator {
    background-color: #ecf0f3;
    padding: 15px;
    border-radius: 30px;
    box-shadow: 12px 12px 20px #cbced1, -12px -12px 20px #ffffff;
    display: grid;
    grid-template-columns: repeat(4, 68px);
}

input {
    grid-column: span 4;
    height: 70px;
    width: 260px;
    background-color: #ecf0f3;
    box-shadow: inset 8px 8px 8px #cbced1, inset -8px -8px 8px #ffffff;
    border: none;
    border-radius: 30px;
    color: rgb(70, 70, 70);
    font-size: 50px;
    text-align: end;
    margin: auto;
    margin-top: 40px;
    margin-bottom: 30px;
    padding: 20px;
}

button {
    height: 48px;
    width: 48px;
    /* background-color: #c5e4fc; */
    box-shadow: 5px 5px 8px #00000020, -5px -5px 8px #ffffff;
    transition: .1s;
    border: none;
    border-radius: 50%;
    margin: 8px;
    font-size: 16px;
}

button:hover {
    box-shadow: inset 5px 5px 8px #00000020, inset -5px -5px 8px #fff;
    background: #fff;
}

.equal {
    width: 115px;
    border-radius: 40px;
    font-size: 21px;
    background-color: #f79a06;
    box-shadow: 5px 5px 8px #00000020, -5px -5px 8px #ffffff;
    color: #fff;
}

.equal:hover {
    width: 115px;
    border-radius: 40px;
    box-shadow: inset 5px 5px 8px #ffab24, inset 0px 0px 8px #f5ad39;
    background: rgb(255, 145, 0);
}

.clear_button {
    background: #33cc33;
    color: #fff;
}

.clear_button:hover {
    box-shadow: inset 5px 5px 8px #2eb82e, inset 2px 2px 8px #33cc33;
    background: #33cc33;
}

.operator {
    color: #ffab24;
    font-weight: bold;
    font-size: 18px;
}

.operator:hover {
    color: #ff9e02;
}

.basic_footer span {
    background-color: #9de2ee;
    margin-bottom: 0px;
    padding: 5px;
    font-size: 18px;
    color: black;
    justify-content: center;
    text-align: center;
    /* overflow: auto; */
}